Index: head/sys/boot/zfs/zfsimpl.c
===================================================================
--- head/sys/boot/zfs/zfsimpl.c
+++ head/sys/boot/zfs/zfsimpl.c
@@ -929,7 +929,7 @@
 {
 	vdev_t vtmp;
 	vdev_phys_t *vdev_label = (vdev_phys_t *) zap_scratch;
-	vdev_phys_t *tmp_label = zfs_alloc(sizeof(vdev_phys_t));
+	vdev_phys_t *tmp_label;
 	spa_t *spa;
 	vdev_t *vdev, *top_vdev, *pool_vdev;
 	off_t off;
@@ -957,6 +957,12 @@
 	psize = P2ALIGN(ldi_get_size(read_priv),
 	    (uint64_t)sizeof (vdev_label_t));
 
+	/* Test for minimum pool size. */
+	if (psize < SPA_MINDEVSIZE)
+		return (EIO);
+
+	tmp_label = zfs_alloc(sizeof(vdev_phys_t));
+
 	for (l = 0; l < VDEV_LABELS; l++) {
 		off = vdev_label_offset(psize, l,
 		    offsetof(vdev_label_t, vl_vdev_phys));
@@ -988,6 +994,9 @@
 
 	zfs_free(tmp_label, sizeof (vdev_phys_t));
 
+	if (best_txg == 0)
+		return (EIO);
+
 	if (vdev_label->vp_nvlist[0] != NV_ENCODE_XDR)
 		return (EIO);